A small intelligence agency, the Public Security Investigation Agency of the Ministry of Justice, handles national security matters both inside and outside the country. Mainly involved in counter-espionage, its activities are not generally known to the public. The Koancho was set up in 1952 as an agency to investigate and control internal subversion. It is staffed by some 1,800 investigators. Its activities focus mainly on the far left and right, as well as the Japan Communist Party, which was its main target during its early years. In addition, it is probably the single group in Japan that is most responsible for surveillance of resident Koreans At present, it is focusing its surveillance on Aum Shinrikyo, partly in a move to gain increased legitimacy.
With the Subversive Activities Prevention Law coming into force on 21 July 1952, Public Security Investigation Agency was established on the same date based on this law as an executive organization which is tasked to execute comprehensive duties that include conducting of investigations and requesting for action in reference to control of subversive organizations based on the provisions of the law. The Subversive Activities Prevention Law has objectives of taking such measures as control of activities or even dissolution of such organizations as deemed necessary, imposing appropriate penalty to individuals who committed violent subversive activities, and protecting democracy, basis of the Japanese people to enjoy peaceful and secured living.
The Public Security Investigation Agency comprises internal departments, an institute, regional bureaus and prefectural offices. Internal departments are the General Affairs Department, First Investigation Department and Second Investigation Department, institute being the Training and Research Institute and there are eight (8) regional Public Security Investigation Bureaus and forty-three (43) prefectural Public Security Investigation Offices throughout the country as field offices.
The Public Security Investigation Agency is set up with the purpose of contributing to insuring security of the public. Among its key tasks are to conduct investigations based on the Subversive Activities Prevention Law into organizational structure and activities of organizations that harbor intentions of destroying the democratic system guaranteed by the Japanese Constitution through violent means, and in the event it was determined that the results of investigations meet the requirement of the law, and that some control measures including dissolution are necessary, it is the task of the Public Security Investigation Agency to forward a request for control measures to the Public Security Examination Commission.
The control of organization is an administrative measures to be taken against an organization that ignored the fundamental law and order provided by the Constitution, carried out violent subversive activities, and there remains apprehensions that the organization may in the future carry out similar activities. The control of organization included restriction of specific activities and dissolution of organization.
In order to conduct investigations needed for control of a subversive organization, Public Security Investigation Agency has public security investigators stationed throughout the country. The public security investigators are conferred an investigative authority by the Subversive Activities Prevention Law. This investigative authority has no compulsory power such as to seize evidence or to search houses, but limited to optional basis.
By the early 1990s, with internal ultra leftists' activities gradually fading, PSIA lost its main role. That was the time when AUM Supreme Truth caused Tokyo Gas Attack. PSIA, having no file and data about AUM in adbance, rushed to investigate the cult and so, in 1995 winter, managed to be ready for applying "the Subversive Acitivies Prevention Law". PSIA has established a position as authority about AUM related problems. However, because of insufficient evidence, the Publice Security Examination Commission eventually rejected PSIA's appeal to disband AUM.Under the administrative reform since 1996, the Japanese government decided that PSIA should be reduced in size and, in turn, a part of the staff should be allocated to other organizations -- that is, the Cabinet Intelligence Research Office and the Ministry of Foreign Affairs. Those PSIA staff are to be sent to foreign countries in order to strengthen overseas intelligence activities of Japan.Current there are 1,700-1,800 members of PSIA, which will eventually be decreased to at most 1,100. The other 600-700 staff will be assigned to these other agencies. The Second Department of Investigation is in charge of foreign intelligence. The Division 2-2 has liaison contacts with over 30 intelligence agencies in the world, including CIA, FBI, MI6, MOSSAD and so on. The US Central Intelligence Agency has invited PSIA officials for training in Washington D.C., in the Intelligence Analysis Course. An "external organization" called Kyudankai had the function of analyzing information (and conducting espionage) on military movements in the Soviet Union. This group reportedly had knowledge of the impending 1980 invasion of Afghanistan, and communicated these suspicions to the Japanese government.